The invention relates to a biosensor, and more specifically to a biosensor measuring penicillin G concentration and systems comprising the same.
Penicillin is an antibiotic produced from penicillinum. Penicillin binding protein (PBP) is an essential enzyme used in synthesizing bacteria cell walls. When penicillin combines with PBP, synthesis of bacteria cell walls is inhibited. This is because PBP cannot supply enough proteins to synthesize bacteria cell walls after penicillin and PBP are combined, finally resulting in breakdown and death of cells.
Penicillin may cause serious allergies in 10˜20% of the population, thus, it is advantageous to develop a method of detecting penicillin residue in food or cosmetics. Currently, penicillin residue can be detected using enzymes capable of decomposing penicillin, with the enzyme usually immobilized on a substrate. Enzyme immobilization can be accomplished using chemical and physical methods. A chemical method is disclosed in U.S. Pat. No. 6,060,268. A penicillin G acylase is immobilized on a cross-linked mixture by covalent bonds, wherein the cross-linked mixture comprises gelled gelling agents, such as gelatin, and a polymer containing free amino groups, such as alginate, amine, chitosan, or polyethylene imine.
Another chemical method is disclosed in U.S. Pat. No. 5,780,260. Penicillin G amidase, glutaryl-7-ACA acylase, or D-amino acid oxidase is immobilized on an amino-functional organosiloxane polymer carrier by covalent bonds. The covalent bonds are formed by activating amino groups on the carrier with a dialdehyde and reacting the activated groups with reactive groups on the enzyme.
A strong chemical bond may be formed between an enzyme and a monomer using the chemical methods. The chemical methods, however, have several drawbacks, for example, are expensive and complicated, and enzyme activity may easily be lost since an enzyme activity center usually participates in bonding. Physical methods are simple and conventionally used, but also have problems of enzyme loss due to no formation of covalent bonds.
A method of detecting penicillin concentration is disclosed in U.S. patent Ser. No. 10/028,079. A penicillinase is immobilized on a pH-sensitive hydrogel. When penicillic acid is produced by decomposing penicillin using the penicillinase, osmotic pressure of the hydrogel may alter as concentration of the penicillic acid alters. Penicillin concentration may thus be obtained by detecting variation of osmotic pressure using a pressure transducer. The method, however, may consume energy due to use of the pressure transducer, resulting in non-accurate measurement.